The Sol System is a Solar System and the nursery of the human race. It has a G2 type star at the center surrounded by 4 rocky inner planets, an asteroid belt, 4 gas giants, the Kuiper Belt and the Oort Cloud.
The Sun (Sol)
The Sun is an ordinary G2 star, and the largest object in the solar system. It contains more than 99.8% of all the matter in the Solar System.
The Sun is -- at present -- about 75% Hydrogen and 25% Helium (by mass), this will change as the Sun changes Hydrogen to Helium through fusion at its core. This fusion produces 386 billion billion Megawatts of power, as it converts 700 million tonnes of Hydrogen into 695 million tonnes of Helium every second. The Sun is about 4.5 billion years old, and will radiate peacefully for another 5 billion as it becomes almost twice as bright. Eventually, the Sun will run out of Hydrogen causing it to change radically, leading to the destruction of all the Inner Planets.
The Inner (or Terrestrial) planets are composed primarily of rock and metal, and have relatively high densities, slow rotation, solid surfaces no rings and few satellites.
Mercury is the closest planet to the Sun, and the eight largest. It orbits the sun at a mean distance of 0.38AU, has a mass of 3.30x1023kg and a diameter of 4878km.
Mercury's orbit is highly eccentric, and was original explained with the postulation of an inter-mercurial planet (Vulcan). However, with Einstein's General Theory of Relativity, the perturbations were finally explained eliminating the necessity of discovering an imaginary planet.
Mercury's interior is dominated by a large iron core whose radius is 1800 to 1900km thick. The silicate outer shell is only 500 to 600km thick. This composition gives Mercury the second highest density in the solar system, after the Earth. In fact, if Mercury were as large as Terra, it would be denser than her.
Venus is the second planet from Sol and the sixth largest. Its orbit is the most circular with an eccentricity of less than 1% with a mean radius of 0.72AU. Venus has a diameter of 12103.6km and a mass of 4.869x1024kg.
Venus's rotation is unusual in two ways: it is retrograde (it rotates in the opposite direction of the rest of the planets), and it is slow (243 Terran days per 1 Venus day).
Venus is sometimes regarded as Terra's sister planet due to size and chemical composition; however, they are also very different. Venus' atmospheric pressure at the surface is 90 times that of Terra at sea level. This pressure cooker atmosphere is mainly composed of carbon dioxide and sulfuric acid at temperatures between 400 and 750K.
The Earth is home to mankind, and is the third rock from the sun. She orbits Sol at a mean distance of 1.00AU (by definition -- 149.6 MSKm). Earth's mass is 5.976x1024kg and has a diameter of 12756km.
Unlike other terrestrial planets, Earth's crust is divided in several separate solid plates which float around on top of the hot mantle below. The theory that describes this is known as plate tectonics. The interaction of these plates are what creates the geologic-ally active topography of our home world.
The Earth has a single satellite:
- The Moon (Luna). It orbits the Earth at a mean distance of 384000km, has a radius of 1738km and a mass of 7.35x1022kg. Due to its close orbit, Luna is tidally locked with the Earth; and thus always shows the same side.
Luna has the distinction of being the only terrestrial body to be visitedby humans (on July 20 1969). Man will eventually have to return to mine the He3 left on the surface by the solar wind.
Mars is the fourth planet from the sun and the seventh largest. It orbits the sun at a distance of 1.52AU, has a diameter of 6794km and a mass of 6.4219x1023kg. Mars' orbit is significantly elliptical, giving it a temperature variation of about 30C at the sub-solar point.
Although much smaller than Terra, Mars has a surface area equal to the land surface are of the Earth. It also has a highly varied and interesting terrain (second only to Earth):
- Olympus Mons: The largest mountain in the Solar System rising 24km about the surrounding plain.
- Tharsis: A huge bulge on the Martian surface that is 4000km across and 10km high.
- Valles Marineris: A system of canyons 4000km long and 2 to 7km deep.
- Hellas Planitia: An impact crater in the southern hemisphere of 6km deep and 2000km in diameter.
Mars has two potato shaped moons that were discovered by Hall in 1877:
- Phobos: Orbiting Mars at a distance of 9000km, with a radius of 11km and a mass of 1.08x1016kg.
- Deimos: Orbiting Mars at a distance of 23000km, with a radius of 6km and a mass of 1.80x1015kg
More than 6000 asteroids have been discovered so far, and hundreds more are discovered each year. There are 26 known asteroids more than 200km across, but total mass of all the asteroids does not surpass the mass of the Moon (Luna). Jovian Planets
The Jovian (or Gas Giant) planets are composed primarily of hydrogen and helium and generally have low densities, rapid rotation, deep atmospheres, rings and lots of satellites.
Jupiter is the fifth planet from the sun and the largest. Jupiter is more than twice as massive as all the other planets combined. It orbits the sun at a mean distance of 5.20AU, has a diameter of 142984km and a mass of 1.900x2027kg.
Jupiter has the following satellites:
Saturn is the sixth planet from the sun and second largest. It orbits the sun at a mean distance of 9.54AU, has a diameter of 120536km and a mass of 5.688x1026kg.
Saturn is the least dense of the planets, and is famous for its huge ring system. Though they look continuous from Earth, the rings are actually composed of innumerable small particles each in an independent orbit. They range in size from a centimeter or so, to several meters.
Saturn has an extensive moon system:
Uranus is the seventh planet from the Sun and the third largest (by diameter, although it is lighter than Neptune). It orbits the Sun at a mean distance of 19.218AU, has a diameter of 51118km and a mass of 8.686x1025kg.
Uranus is about 83% hydrogen, 15% helium and 2% methane. Like most gas giants, Uranus has rings and bands of rapidly blowing clouds. Uranus' blue color is the result of the absorption of red light by methane in the upper atmosphere.
Uranus has an extensive moon system:
Neptune is the eight planet from the eighth planet from the sun and fourth largest (by diameter). It orbits the sun at a mean distance of 30.06AU, has a diameter of 49528km and a mass of 1.0247x1026kg.
Like Jupiter and Saturn, Neptune has an internal heat source and radiates more than twice as much energy as it receives from the Sun. However, like Uranus (but unlike Jupiter and Saturn) it is likely to be uniform in composition and not have distinct layers.
Neptune has an extensive moon system:
The Kuiper Belt is a disk-shaped region past the orbit of Neptune reaching into the Oort Cloud (30AU to 100AU) containing many small icy bodies. It is the source of short-period comets.
It is estimated that there are 35,000 Kuiper Belt objects greater than 100km in diameter, which is several hundred times the number and mass of similar sized objects in the asteroid belt.
Pluto and Charon
Pluto was once considered the furthest planet from the Sun, but is now categorized as a Minor Planet. It orbits the sun at a mean distance of 39.5AU, has a diameter of 2340km and a mass of 1.32x1022kg.
Pluto and its companion Charon are a "double" minor planet due to their relative sizes. Charon has a diameter of 1260km and a mass of 1.47x1021kg. Before it was discovered that there were two objects, it was thought that Pluto was much larger than it really is since the images has the two bodies blurred together.
Pluto and Charon both rotate synchronously about each other, so that they both keep the same face towards one another.
The Oort cloud is a huge spherical "cloud" of perhaps a trillion (1x1012) comets that orbit the Sun far beyond the orbit of Pluto. The Inner Oort cloud starts at about 100AU and ends at about 30000AU. The Outer Oort Cloud begins at about 30000AU and ends about 1LY from the Sun.
The Oort Cloud may account for a significant fraction of the mass of the solar system, perhaps as much as (or even more than) Jupiter.